1. Field of the Invention
The present invention relates to an actuator for converting rotary motion generated by a rotary driving source into rectilinear motion so that a slider is displaced in accordance with an action of the rectilinear motion.
2. Description of the Related Art
An actuator based on the use of a feed screw has been hitherto used as a driving source for transporting a workpiece or the like. As shown in FIG. 26, for example, such an actuator 10 comprises a ball screw 16 provided on a rotary shaft of a motor 12, and a displacement member 18 meshed with the ball screw 16. A guide section 22 of a frame 20 is engaged with the displacement member 18 to prevent the displacement member 18 from rotation. When the motor 12 is operated, the rotary motion of the ball screw 16 is converted by the displacement member 18 into the rectilinear motion. Thus, the displacement member 18 is displaced along the guide section 22.
However, in the case of the actuator 10 concerning the conventional technique as described above, it is feared that the lubricating oil or the like adhered to the ball screw 16 may be scattered, and the working environment may be polluted therewith. For this reason, a problem arises in that such an actuator 10 cannot be used, for example, in the environment to be kept away from dust or the like, such as those in a clean room to be used for the steps of producing semiconductor products. In order to avoid such an inconvenience, it is conceived that the ball screw 16 is covered with a bellows-shaped cover. However, such a cover involves a problem in that it has poor durability.